I will use it for planetary and deep sky observations with my Mak150, C8 and 12” Dobson.

whereas for the deep sky I don’t care about seeing a reflected image, for the moon it is mandatory for me to see it right. And I will not neglect a terrestrial use, neither.

So I need a (good but not too expensive!) erecting diagonal.

the MaxBright comes with all the Baader adapter arsenal so it would be nice to have an Amici or other erecting prism with thread rings. But it is not strictly required.

what I need is an erecting 90 diagonal (or even better 45 deg) with enough quality for astronomic use, for at least moon observation. For deep sky and planetary I will use direct or dielectric mirrors.

The William Optics 45 degree unit is the only quality commercial one that I've tried and it was good. All the others have been the common stock variety which are OK but drop off at high powers. The one I use most for lunar observation is a homemade 90 degree version built round a military spec prism.

The William Optics 45 degree unit is the only quality commercial one that I've tried and it was good. All the others have been the common stock variety which are OK but drop off at high powers. The one I use most for lunar observation is a homemade 90 degree version built round a military spec prism.

Hi Peter, unfortunately I cannot get a military grade one

But about WO diagonal, have you used it for astronomy and what subject did you observe? Any other remark or consideration about it? Can you send me the link to the exact model?

@annoluce. The WO erecting diagonal is sold by First Light Optics and 365Astronomy in the UK, Google will show other vendors. As far as I know it is the only 2" 45 degree unit that WO supplies. Outlets like Surplus Shed in the USA might well list pre-used military spec prisms. This design of prism can give spikes on stars and planets at the centre of the field so are at their best for lunar and terrestrial observation.

For astro use I don't know any 45º erecting prism suitable. All induce too much image quality loss...

As your telescopes are long focal length and with the MaxBright you will have already a small usable FOV for terrestrial use, so the 1st solution should be avoided since increases 2x the focal length.

The second solution should be the best (since is the shorter optical path), but I remember Denis preferring a lower cost version of Baader, for Bino use, but I don't remember which was and if it was a diagonal instead...

In case you consider straight view you might be interested on having a look at http://www.pt-ducks....#CR-binoviewing and http://www.pt-ducks.... image erectors - I found recently a compact erector to use with a binoviewer for terrestrial use and straight view, but I'm still waiting for some adapter pieces I ordered... Will update my page when receiving these and will post here at CN.

For the moment I'm not using any prism, I crane my neck and use the binos directly. The image is better and erected. Not the solution I want for long sessions though. I will carefully look around to quality Amici prisms, as they are needed also for terrestrial use.

I'm happy with my MaxBright so far, for its cost, I believe the quality is ok.